1. Field of the Invention
The present invention relates to a technique of fixing an external electrode in a high-voltage semiconductor power module.
2. Description of the Background Art
Semiconductor power modules used in electric railroads and others include those that require a high rated voltage (of 6500 V or higher) to bring about an advantage in constructing power units (as disclosed in Japanese Patent Application Laid-Open No. 2009-88218). Such semiconductor power modules should maintain isolation between a high-voltage part (collector) and a low-voltage part (emitter or gate).
In the case of an IGBT module, the IGBT module includes a collector main electrode, and a collector external electrode for connecting the collector main electrode to the outside that function as the high-voltage part. The collector external electrode is fixed by press fitting into a resin case to construct a power module, for the reason that this allows manufacture of the power module at low cost, for example.
However, the case may expand due to heat generation during the assembly so the fixation of the collector external may be loosened. As a result, the collector external electrode may be made unsteady, so it cannot be fixed securely in a final product.